<?php
$testing; // declare without assigning
echo "is null".is_null($testing); // checks if null
echo "<br/>";
$testing = 5;
echo "is an interger? ".is_int($testing); // check is integer
echo "<br/>";
$testing = "five";
echo "is an string? ".is_string($testing); // check is string
echo "<br/>";
$testing = 5.024;
echo "is a double? ".is_double($testing); // check is double
echo "<br/>";
$testing = true;
echo "is an boolean? ".is_bool($testing); // check is boolean
echo "<br/>";
$testing = array('apple', 'orange', 'pear');
echo "is an array? ".is_array($testing); // check is array
echo "<br/>";

echo "is an numeric? ".is_numeric($testing); // check is numeric
echo "<br/>";
echo "is an resource? ".is_resource($testing); // check is resource
echo "<br/>";
echo "is an array? ".is_array($testing); // check is array
echo "<br/>";

?>